ofproto: Correctly report table miss configuration in table stats.

OFPTC11_TABLE_MISS_MASK isn't a valid value at all, let alone always the
value in use.  We should report the value actually in use, as this commit
does.

There is a remaining problem: the default table configuration is
OFPROTO_TABLE_MISS_DEFAULT, which doesn't correspond to any particular
OFPTC11_* value or, more precisely, corresponds to a different OFPTC11_*
value based on the OpenFlow version.  The following commit fixes that
problem.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>